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Shop problems in sheet metal for secondary schools
SHOP PROBLEMS IN SHEET METAL FOR SECONDARY SCHOOLS
WITH NOTES ON EQUIPMENT, MATERIALS AND SHOP METHODS
BY EUGENE C. GRAHAM
PRINTED ON THE HIGH SCHOOL PRESS EVANSVILLE, INDIANA, 1918
DOWNLOAD OLD SHEET METAL BOOK:
Shop problems in sheet metal for secondary schools
THE TRADE OF THE SHEET METAL WORKER
As an introduction to this little collection of notes and drawings the author wishes to call the attention of High School boys especially to the fact that this trade has not received the attention it deserves from the schools. In recent years several vocations such as printing, concrete construction, automobile repair and electrical work have found a place in the schools while others seem to be losing ground. It seems to be true that trades such as blacksmithing and molding which have been influenced by the introduction of new machinery which is more or less automatic, have become less attractive to boys.
Sheet metal work as a vocation has many attractive features. It is a large and growing industry represented both in the building trades and in modern automobile construction, furniture and boat building and in the construction of manufactured articles. The introduction of autogenous welding and electric welding has done much to make possible the use of sheet metal in new forms.
All well trained sheet metal workers can draft their own patterns. Boys who have been unable to see any use for intersections and developments in mechanical drawing can quickly see the relation between this branch of drawing and the drafting of patterns.
The working of metal in sheet form is light, interesting and instructive. The making of kitchen utensils, such as pans, sugar scoops, funnels, dustpans, canteens, bread boxes and other articles is attractive to most boys. A large number of hand operated machines are used and the training afforded by these machines is valuable. Boys like wood turning because they can run the machines for themselves. In the same way they become interested in the machines used - to bend and shape sheet metal and can make a larger variety of useful products than in nearly any other school shop.
Boys who are interested in the trade will find that the wages paid are better than in some other related trades and that there is always a demand for competent men.
The author hopes to add to this collection of drawings from time to time and will welcome suggestions and criticisms. The notes are merely a bare outline of related facts and should be supplemented by outside reading and visits to shops where sheet metal is used. Credit is due the Peck, Stow and Wilcox Co., of Southington, Conn., for the electrotypes used.
Sheet metal work as a vocation has many attractive features. It is a large and growing industry represented both in the building trades and in modern automobile construction, furniture and boat building and in the construction of manufactured articles. The introduction of autogenous welding and electric welding has done much to make possible the use of sheet metal in new forms.
All well trained sheet metal workers can draft their own patterns. Boys who have been unable to see any use for intersections and developments in mechanical drawing can quickly see the relation between this branch of drawing and the drafting of patterns.
The working of metal in sheet form is light, interesting and instructive. The making of kitchen utensils, such as pans, sugar scoops, funnels, dustpans, canteens, bread boxes and other articles is attractive to most boys. A large number of hand operated machines are used and the training afforded by these machines is valuable. Boys like wood turning because they can run the machines for themselves. In the same way they become interested in the machines used - to bend and shape sheet metal and can make a larger variety of useful products than in nearly any other school shop.
Boys who are interested in the trade will find that the wages paid are better than in some other related trades and that there is always a demand for competent men.
The author hopes to add to this collection of drawings from time to time and will welcome suggestions and criticisms. The notes are merely a bare outline of related facts and should be supplemented by outside reading and visits to shops where sheet metal is used. Credit is due the Peck, Stow and Wilcox Co., of Southington, Conn., for the electrotypes used.
MATERIALS USED BY THE SHEET METAL WORKER.
Articles made of sheet metal are commonly made either of tin plate, sheet iron or galvanized iron. Other kinds of sheet metal sometimes used, are sheet copper, sheet aluminum, sheet zinc or sheet brass. Each of these materials has some special advantages but it may be said that if we could neglect the item of first cost either sheet copper or sheet aluminum would take the place of most of the other materials. A short paragraph on the qualities of each of the above materials is given below.
Tin Plate
It is often a surprise to a pupil to find that even good tin plate is not made of pure tin. Since it is covered with a metal so different from iron in appearance it is not easily discovered that it is made of sheets of iron covered on both sides with a coating of tin. The thickness of this coating varies somewhat with the quality but it is never very thick. It is put on by dipping plates of iron which have been carefully cleaned in acid and scrubbed with sand and water, into tanks of melted tin. The tin forms a kind of an alloy with the iron in the plate and after passing through the bath of tin one or more times and being carefully cleaned and inspected it becomes a sheet of tin plate.
Tin plate is easily worked, is not easily affected by air or water, takes solder well and can be kept bright and clean without much trouble. It is the cheapest material used for kitchen ware.
Sheet Iron
Plates of soft sheet iron are used for roasting pans, stove pipe and as a lining for ovens. When of nearly pure iron and treated with a process to prevent rust it becomes a good material for limited uses. It cannot be soldered and is easily affected by water and acids.
Galvanized Iron
Galvanized iron is sheet iron or steel coated with zinc, somewhat as tin plate is coated with tin. The zinc coating makes it rust proof for a long time and gives it a pleasing appearance. However the zinc will not stand acids and is likely to peel off in flakes if the metal is hammered or bent. It does not polish well but can be kept clean by washing. It is not used in making kitchen ware but for dry measures, roofing, etc it is in common use.
Galvanized sheets are usually 30 inches wide and 96 inches long. Wider and longer sheets may be bought. The thickness runs from 16 wire gauge or thicker down to 30 wire gauge. Galvanized sheets from 24 to 30 gauge are most commonly used in schools.
Sheet Copper
This metal comes in sheets nearly pure and can be had in many thicknesses and sizes. When used by the sheet metal worker it has many fine qualities and can be drawn, hammered, soldered, and pressed into many shapes. It is tough and stands working better than most metals. It can be annealed or made soft by heating and quenching in water. When made into utensils it is usually tinned and often nickel plated on the outside of the vessel. Pure copper is somewhat acted on by the air and by water and more by acids, so that tinning is necessary for some purposes. On account of the cost it is not much used, but is a very durable roofing material. Copper is used for many articles which are beaten into shape by hammering.
Sheet Zinc.
This metal has many valuable qualities and is used for roofing, tops for kitchen cabinets, ornamental vases, etc. It is very little acted on by the air after the first film of oxide forms on the surface. It may be soldered if care is taken to avoid burning through the metal with a copper which is too hot. Dilute muriatic acid is used as a flux in soldering zinc.
Sheet Brass.
Sheet brass has many of the qualities of copper. It is somewhat harder an requires more care in bending. By annealing it carefully it may be worked into many shapes. Borax may be used as a flux in soldering brass. Because of the increased cost it is not much used except in some manufactured articles such as automobile lamps.
Sheet Aluminum.
This metal is coming into very general use for kitchen utensils. It is very durable and easily kept clean. It is not much acted on by the air or by water and acids, but alkalies have some affect on it. Since its melting point is much lower than that of copper and iron it may be melted through on a hot range if the vessel boils dry. It is very easily worked and may be pressed and drawn into various shapes. Since it cannot be soldered with much success it must either be welded or riveted. Many articles are cast into shape. Aluminum rivets should be used for fastening handles and other attached parts.
The Folding Machine
In order to turn a hem or lock on the edge of a piece of sheet metal some means must be found of holding the metal firmly while the edge is being turned. Or we may grip the edge and turn the fold by moving the piece itself. The ordinary folder does the latter. Other machines are used called open throat folders which use the former method.
These machines will also prepare the edge of sheet metal to receive a wire. All folders have adjustments to regulate the width of the fold and also the sharpness of bend, so that they may also be used to prepare the edge of sheets to receive a wire. It is always necessary to know just how the machine is adjusted before attempting to make a fold or to wire an edge.
The Grooving Machine
After a lock seam has been folded on the folder it should be closed down with a grooved wheel on the grooving machine. Hand tools are also used for this but in all cases where it is possible to use the machine it is better to do so. The grooving rolls are made to fit several widths of seam and the proper roll should be used.
The Brake.
This machine, commonly called the cornice brake, has a wider range of usefulness than the folder. It may be used to turn hems or folds and also to make bends at all angles up to nearly 180 degrees, and at any distance from the edge. The brake also has attachments for forming molded shapes to almost any pat- tern. Lengths up to eight feet are in common use.
In using this machine it is necessary to plan the bends to be made if several are to be turned in the same piece. Otherwise the pupil will find it hard to decide what the order of operations should be.
It is advisable to mark the location of lines and bends with punch marks. A line may thus be transferred to the other side of the sheet accurately.
Foot levers are provided to hold the work temporarily, but it is quite important that the cam levers should be used to clamp the work in place. Pupils should never attempt to bend heavy metal or wire in this machine.
The Wiring Machine.
After the use of the turning machine the wire is fitted to its place and partly closed in with a mallet. Then the wiring machine is used to tuck in the edge of the metal neatly around the wire. Some judgment is needed to set the machine for different sizes of wire.
This machine may also be used to wire the edges of flat work. Pains should be taken to keep the surface of the flat work horizontal or to raise the outer edge a little in order to prevent a ridge being formed on the lower side of the work.
The Turning Machine
Turning machines are used to prepare the edge of a can body or other similar work such as the edge of a funnel to receive a wire. When such work is ready it is placed on the lower grooved roll and against the gauge. The screw is turned until the upper roll forms a slight groove in the work. After one revolution the work is tilted upward a little and the screw tightened until a deeper groove is formed. By repeating this operation and making several revolutions of the work the edge is prepared to receive the wire. To avoid some of the most common faults of beginners, try to turn slowly at first and to press the work firmly against the gauge. After tilting the work upward do not allow it to' drop back again. Do not force the rolls against the metal. Practice on some can bodies which have been cut down from discarded tomato cans to a height of about three inches. Serviceable tin cups may be made of these by wiring the top edge and soldering on a neat handle. Skill will come with practice.
The Burring Machine
This machine is used for turning an edge on cylinders of metal or on discs such as can bottoms. In preparing vessels for double seaming a burr is first turned at a right angle on the body and then one of the same width on the edge of the bottom. This last operation is quite difficult and takes considerable practice. Bottoms can be made much better on a circular shear with a flanging attachment.
In using the burring machine remember that only a narrow burr about one eighth of an inch wide can be turned. The burring machine is the hardest machine for beginners to use. The pupil should avoid spoiling good material until he has had careful instruction.
The Setting Down Machine
This is used to close the seams left by the burring machine. It is very simple and may be turned in either direction. It has no adjustments except for thickness of material.
Tin Plate
It is often a surprise to a pupil to find that even good tin plate is not made of pure tin. Since it is covered with a metal so different from iron in appearance it is not easily discovered that it is made of sheets of iron covered on both sides with a coating of tin. The thickness of this coating varies somewhat with the quality but it is never very thick. It is put on by dipping plates of iron which have been carefully cleaned in acid and scrubbed with sand and water, into tanks of melted tin. The tin forms a kind of an alloy with the iron in the plate and after passing through the bath of tin one or more times and being carefully cleaned and inspected it becomes a sheet of tin plate.
Tin plate is easily worked, is not easily affected by air or water, takes solder well and can be kept bright and clean without much trouble. It is the cheapest material used for kitchen ware.
Sheet Iron
Plates of soft sheet iron are used for roasting pans, stove pipe and as a lining for ovens. When of nearly pure iron and treated with a process to prevent rust it becomes a good material for limited uses. It cannot be soldered and is easily affected by water and acids.
Galvanized Iron
Galvanized iron is sheet iron or steel coated with zinc, somewhat as tin plate is coated with tin. The zinc coating makes it rust proof for a long time and gives it a pleasing appearance. However the zinc will not stand acids and is likely to peel off in flakes if the metal is hammered or bent. It does not polish well but can be kept clean by washing. It is not used in making kitchen ware but for dry measures, roofing, etc it is in common use.
Galvanized sheets are usually 30 inches wide and 96 inches long. Wider and longer sheets may be bought. The thickness runs from 16 wire gauge or thicker down to 30 wire gauge. Galvanized sheets from 24 to 30 gauge are most commonly used in schools.
Sheet Copper
This metal comes in sheets nearly pure and can be had in many thicknesses and sizes. When used by the sheet metal worker it has many fine qualities and can be drawn, hammered, soldered, and pressed into many shapes. It is tough and stands working better than most metals. It can be annealed or made soft by heating and quenching in water. When made into utensils it is usually tinned and often nickel plated on the outside of the vessel. Pure copper is somewhat acted on by the air and by water and more by acids, so that tinning is necessary for some purposes. On account of the cost it is not much used, but is a very durable roofing material. Copper is used for many articles which are beaten into shape by hammering.
Sheet Zinc.
This metal has many valuable qualities and is used for roofing, tops for kitchen cabinets, ornamental vases, etc. It is very little acted on by the air after the first film of oxide forms on the surface. It may be soldered if care is taken to avoid burning through the metal with a copper which is too hot. Dilute muriatic acid is used as a flux in soldering zinc.
Sheet Brass.
Sheet brass has many of the qualities of copper. It is somewhat harder an requires more care in bending. By annealing it carefully it may be worked into many shapes. Borax may be used as a flux in soldering brass. Because of the increased cost it is not much used except in some manufactured articles such as automobile lamps.
Sheet Aluminum.
This metal is coming into very general use for kitchen utensils. It is very durable and easily kept clean. It is not much acted on by the air or by water and acids, but alkalies have some affect on it. Since its melting point is much lower than that of copper and iron it may be melted through on a hot range if the vessel boils dry. It is very easily worked and may be pressed and drawn into various shapes. Since it cannot be soldered with much success it must either be welded or riveted. Many articles are cast into shape. Aluminum rivets should be used for fastening handles and other attached parts.
The Folding Machine
In order to turn a hem or lock on the edge of a piece of sheet metal some means must be found of holding the metal firmly while the edge is being turned. Or we may grip the edge and turn the fold by moving the piece itself. The ordinary folder does the latter. Other machines are used called open throat folders which use the former method.
These machines will also prepare the edge of sheet metal to receive a wire. All folders have adjustments to regulate the width of the fold and also the sharpness of bend, so that they may also be used to prepare the edge of sheets to receive a wire. It is always necessary to know just how the machine is adjusted before attempting to make a fold or to wire an edge.
The Grooving Machine
After a lock seam has been folded on the folder it should be closed down with a grooved wheel on the grooving machine. Hand tools are also used for this but in all cases where it is possible to use the machine it is better to do so. The grooving rolls are made to fit several widths of seam and the proper roll should be used.
The Brake.
This machine, commonly called the cornice brake, has a wider range of usefulness than the folder. It may be used to turn hems or folds and also to make bends at all angles up to nearly 180 degrees, and at any distance from the edge. The brake also has attachments for forming molded shapes to almost any pat- tern. Lengths up to eight feet are in common use.
In using this machine it is necessary to plan the bends to be made if several are to be turned in the same piece. Otherwise the pupil will find it hard to decide what the order of operations should be.
It is advisable to mark the location of lines and bends with punch marks. A line may thus be transferred to the other side of the sheet accurately.
Foot levers are provided to hold the work temporarily, but it is quite important that the cam levers should be used to clamp the work in place. Pupils should never attempt to bend heavy metal or wire in this machine.
The Wiring Machine.
After the use of the turning machine the wire is fitted to its place and partly closed in with a mallet. Then the wiring machine is used to tuck in the edge of the metal neatly around the wire. Some judgment is needed to set the machine for different sizes of wire.
This machine may also be used to wire the edges of flat work. Pains should be taken to keep the surface of the flat work horizontal or to raise the outer edge a little in order to prevent a ridge being formed on the lower side of the work.
The Turning Machine
Turning machines are used to prepare the edge of a can body or other similar work such as the edge of a funnel to receive a wire. When such work is ready it is placed on the lower grooved roll and against the gauge. The screw is turned until the upper roll forms a slight groove in the work. After one revolution the work is tilted upward a little and the screw tightened until a deeper groove is formed. By repeating this operation and making several revolutions of the work the edge is prepared to receive the wire. To avoid some of the most common faults of beginners, try to turn slowly at first and to press the work firmly against the gauge. After tilting the work upward do not allow it to' drop back again. Do not force the rolls against the metal. Practice on some can bodies which have been cut down from discarded tomato cans to a height of about three inches. Serviceable tin cups may be made of these by wiring the top edge and soldering on a neat handle. Skill will come with practice.
The Burring Machine
This machine is used for turning an edge on cylinders of metal or on discs such as can bottoms. In preparing vessels for double seaming a burr is first turned at a right angle on the body and then one of the same width on the edge of the bottom. This last operation is quite difficult and takes considerable practice. Bottoms can be made much better on a circular shear with a flanging attachment.
In using the burring machine remember that only a narrow burr about one eighth of an inch wide can be turned. The burring machine is the hardest machine for beginners to use. The pupil should avoid spoiling good material until he has had careful instruction.
The Setting Down Machine
This is used to close the seams left by the burring machine. It is very simple and may be turned in either direction. It has no adjustments except for thickness of material.
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Shop problems in sheet metal for secondary schools
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